A diversity antenna device that selectively uses an antenna element with excellent signal quality is used in a small wireless communication terminal such as a mobile phone.
However, with the miniaturization of mobile phones and other types of antenna devices in recent years, less and less space is afforded to antenna devices, making it difficult to improve the capabilities of antenna devices by reducing the mutual coupling and the correlation coefficient between diversity antenna elements.
Under such circumstances, various antenna devices have been proposed in order to improve the capabilities of antenna devices (for example, refer to U.S. Pat. No. 6,549,170, Japanese Patent Laid-Open No. 2007-13643, and Japanese Patent Laid-Open No. 2008-167421).